1. Field of the Invention
The invention relates to a door lock, and particularly to a door lock including an outside spindle tube connected to an outside handle, an insert tube disposed inside the outside spindle tube and having a latch operating tab, and a clutch to hold together the outside spindle tube and the insert tube for simultaneous rotation or to separate the same for independent rotation of the outside spindle tube from the insert tube.
2. Description of the Related Art
Cylindrical locks generally include inside and outside handles respectively connected to inside and outside spindle tubes to actuate a latch mechanism that controls the opening and closing of a door. The inside spindle tube is provided with a press button, whereas the outside spindle tube incorporates a key-operated lock and an insert tube formed with a latch operating element for operating the latch mechanism so as to control a latch bolt of the latch mechanism. When the press button is pressed, the outside handle and the outside spindle tube are locked from rotation. In this situation, the outside handle and the outside spindle tube can be rotated only after the key-operated lock is actuated by a key. However, in many cases, the user may rotate forcefully the outside handle in the locked state as he/she cannot see whether or not the press button is pressed at the inside of the door. The frequent or forced rotation of the handle in the locked state can damage the interior structure of the door lock.
An improved door lock designed to alleviate the aforesaid problem is suggested in U.S. Pat. No. 5,868,018. In the door lock disclosed therein, an inside inner spindle, which has a latch operating tab and which is inserted into a spindle tube, is movable axially inside the spindle tube so as to be engageable with or disengageable from the spindle tube for simultaneous rotation when an inside press button is not pressed, or for permitting independent rotation of the spindle tube when the press button is pressed at the inside of a door. The spindle tube further receives an inside outer spindle which is axially spaced apart from the inside inner spindle and which is engageable with or disengageable from the inside inner spindle like a clutch. When the inside outer spindle is rotated by an operating shaft projecting from a core or plug of a key-operated lock, the inside outer spindle can rotate the inside inner spindle which is in engagement therewith, thus operating a latch bolt to open the door and releasing the press button from a pressed state.
The object of the present invention is to provide a door lock in which an outside spindle tube can be rotated in a locked state of the door lock.
According to the present invention, a door lock includes: an inside handle incorporating a press button; an outside handle; an outside spindle tube including a first end connected to the outside handle, a second end opposite to the first end, and a first engaging member projecting radially inward from the second end; an insert tube inserted into the outside spindle tube through the second end, and including a third end adjacent the second end, a fourth end extending inside the outside spindle tube, and a latch operating tab which projects from the third end to extend outwardly of the third end and which is adapted to operate a latch operating mechanism, the insert tube further having an inner wall and a second engaging member projecting inwardly from the inner wall; a clutch member disposed inside the insert tube and having an outer peripheral surface formed with first and second axial grooves, the second axial groove engaging the second engaging member of the insert tube, the clutch member being axially movable between a first position in which the first engaging member engages slidably the first groove and a second position in which the first engaging member disengages from the first groove; a spring disposed inside the insert tube to urge the clutch member toward the second end so as to place the clutch member in the first position; and a spindle rod having one end connected to the press button and another end connected to the clutch member so as to move the clutch member to the second position when the press button is pressed.